01
Access and tool geometry
Review internal radii, deep pockets, narrow slots, undercuts, threads and reach against a credible cutting and evacuation route.
Evidence route
Feature-access notes and proposed tool/process route
Machining DFM
CNC design for manufacturability: close the costly ambiguity before release.
CNC DFM should preserve functional intent while reducing avoidable access, setup, tool, stock, distortion and inspection risk. PartVerity records the proposed change, reason, consequence and approval rather than allowing the factory to silently optimise the design.
Decision premise
DFM question: which design details drive risk or cost, and can they change without weakening function, interface or verification?
Engineering control
Six DFM lenses for a controlled machining review
Rules of thumb are orientation only. Material, size, tool access, machine route, tolerance and volume determine whether a detail is actually problematic.
02
Setup and datum count
Identify reorientations, transferred datums and fixture dependencies that affect relationship tolerances and repeatability.
Evidence route
Setup concept, datum map and transfer-critical features
03
Wall and feature stability
Flag thin walls, slender forms, interrupted sections and asymmetric stock removal that can move under heat or clamping.
Evidence route
Support, sequence and free-state inspection plan
04
Tolerance rationalisation
Distinguish function-critical controls from inherited or default precision that adds operations without decision value.
Evidence route
CTQ list, proposed relief and engineering approval status
05
Stock and material route
Review stock form, allowance, grain/orientation where relevant, certificate needs and finish/heat-treatment sequence.
Evidence route
Material route and pre/post-process dimensional basis
06
Change control
Keep every DFM proposal tied to the affected requirement, rationale, visual evidence, response and accepted revision.
Evidence route
Numbered DFM log, disposition owner and revision closure
Decision matrix
DFM issue to controlled decision
A useful DFM note identifies consequence and approval impact; it does not simply ask the buyer to ‘increase radius’ or ‘relax tolerance.’
| DFM observation | Decision to make | Closure evidence |
|---|---|---|
| Deep narrow pocket | Change geometry, split route, accept specialist tooling or retain requirement | Access rationale, approved geometry and supplier route |
| Tight relationship across setups | Redesign datum/feature, use combined setup or qualify transfer | Setup/datum plan and feature-specific inspection |
| Thin unsupported wall | Add support/material, stage cutting or accept risk/limit | Sequence, fixture concept and free-state result |
| Blanket tight tolerance | Retain only function-linked CTQs or justify full scope | Engineering disposition and revised drawing |
| Finish changes dimensions | Add allowance, mask feature or inspect after finish | Controlled process sequence and final acceptance result |
Claim boundaries
DFM behaviour PartVerity does not accept
Changing a CAD model without a documented engineering disposition.
Presenting supplier preference as a mandatory design rule.
Quoting a cheaper route that cannot support the inspection requirement.
Closing DFM while drawing and model revisions still disagree.
Technical context
Use guidance to frame the review—not to replace project evidence.
External design orientation for geometry, setup and machining-time trade-offs. Numeric rules remain provider-, material- and geometry-dependent.
Protolabs Network CNC DFM guidance